Paywalls only have to allow you visit their site 3 times a day for free if you come from google [0]. It might not work because you have visited more then 3 articles already today. Deleting your cookies or entering the private mode of your browser should do the trick, though.
It's a by-product of the broken paywall model. Sites want to protect their content, but they still want traffic to their site. Checking that the referrer is a search engine is a weird middle-way workaround.
Most paywalls check the request referral and let it through when it comes from the big search engines. This ensures they will remain listed and hence relevant.